Looking for a laptop, but don't want to pay cutting-edge prices? The Sustainablog has a wise and helpful 10-point checklist to run through when sizing up a used laptop, and ensuring its value after it arrives. For example, the author suggests buying only from a refurbishing manufacturer, an eBay seller with 100% positive feedback (to ensure cooperation), or a Craigslist vendor who's willing to meet in a coffee shop and let you examine the unit on-site. Once that's arranged, make sure you check everything, including the ports:

Check all plugs, sockets, and wireless connections like Bluetooth and Wi-Fi. Many of these are attached to the motherboard, which is costly to replace. If one USB port is broken and you can live with the other three, then do it. If the headphone jack is broken but you have Bluetooth headphones anyway, then rejoice.